1. Field of the Invention
The present invention relates to a method and apparatus for practicing dynamic keratometry and keratoscopy.
2. Description of the Prior Art
Until relatively recently there was no satisfactory means for determining corneal curvature during eye surgery. In the absence of such a means a surgeon could not accurately establish the effects of the eye surgery upon corneal curvature at the actual time of surgery.
In some patients post-operative astigmatism was so great that it was difficult or impossible to satisfactorily correct the astigmatism through the use of glasses or contact lenses.
Richard D. Troutman, M.D., recently advanced a micro-surgical keratometer for evaluating the effects of eye surgery on corneal curvature. The keratometer is rigidly mounted directly to a surgical microscope of the type typically used for eye surgery. A fiberoptic bundle coupled to a light source is utilized to project upon the cornea a circle of discontinuous dots of relatively low light intensity visible to the surgeon when the operating room lights are shut off or dimmed. The microscope controls are operated to focus the circular dot image on the cornea, and the dot image is compared with measurements previously obtained through the use of a clinical quantitative keratometer. The microscope and keratometer are fixed in position to maintain proper image focus while observing, quantitatively, any change in the light dot pattern as the operation proceeds. The degree of distortion of the dot pattern relative to a perfect circle is established by comparing the relationship between the dot pattern and the microscope eyepiece reticles. A flat cornea reflects a dot pattern closer to the outer reticle of the eyepiece, while a steep cornea reflects a dot pattern closer to the inner reticle. The maintenance of the keratometer at a fixed distance from the cornea thus provides a measure of the degree of corneal curvature. Adjusting the cross hairs of the reticle to coincide with the long axis of a reflected oval dot pattern provides reference points for establishing the approximate amount of astigmatism or meridional error present. Since image focus and measurement of the degree of corneal curvature require that the keratometer be fixed, the system is incapable of providing dynamic keratometry. That is, it is not possible to dynamically detect meridional error of all positions of the meridia lying between the corneal center and corneal periphery. The focused dot pattern crosses each corneal meridian at only one point. In this regard, it is noted that the well known clinical Klein keratoscope projects concentric circles which cross each corneal meridia at more than one point. However, there is no means by which such an instrument can be utilized as an integral part of a surgical procedure to establish corneal curvature while the surgery is in progress, nor is the keratoscope adapted for establishing the corneal curvature of those portions of meridia located between the reflected concentric circular images. The keratoscope requires a fixed distance from the eye for focusing.